1. Field of the Invention
This invention relates to a three-dimensional image display system for carrying out multi-parallax stereoscopic display based on a plurality of parallax images.
2. Description of the Related Art
In the past, as a technique for generating a stereoscopic image, a two-eye type stereoscopic image technique wherein images different from each other called parallax images are shown to both eyes of an observer so that the observer can feel a stereoscopic effect and a multi-eye type stereoscopic image technique wherein a plurality of sets of parallax images are prepared such that a stereoscopic image from different viewpoints is provided are available, and various techniques relating to such techniques have been and are being developed very much. However, a stereoscopic image by the techniques described above does not physically exist at an intended position as a stereoscopic image, but, for example, each image exists on a two-dimensional display plane and always exists at a fixed position. From this, particularly convergence and adjustment which are physiologic reactions of the ophthalmencephalon are not linked to each other, and visual fatigue caused by this makes a problem.
Meanwhile, in the real world, information of the surface of a physical solid propagates to the eyeballs of the observer through a light wave serving as a medium. As a technique by which a light wave from a physical solid in the real world can be physically reproduced artificially, a holography technique is available. In a stereoscopic image which uses a holography technique, interference fringes generated by interference of light are used, and a diffracted light wave front itself which is generated when light is illuminated on the interference fringes is used as an image information medium. Therefore, an image with which such physiologic reactions of the ophthalmencephalon as convergence and adjustment similar to those when the observer observes a physical solid in the real world occurs and the visual fatigue is reduced can be provided. Further, that the light wave front from the physical solid is reproduced can be considered that the continuity is assured in a direction in which image information is transmitted. From this, the holography technique is regarded also as an image providing technique by which, as the viewpoint of the observer moves, appropriate images from different angles according to the movement can be presented successively and motion parallaxes are provided successively.
However, according to the holography technique, three-dimensional spatial information is recorded as interference fringes in a two-dimensional space, and the amount of spatial frequencies is very great when compared with that of information of a two-dimensional space on a picked up photograph of the same physical solid or the like. It is considered that this arises from the fact that, when information of a three-dimensional space is converted into information of a two-dimensional space, the information is converted into density in the two-dimensional space. Therefore, the spatial resolution necessary for a device which displays interference fringes by CGH (Computer Generated Hologram) is very high, and a very great amount of information is demanded. Therefore, in the existing condition, it is technically difficult to implement a stereoscopic image with a real time hologram.
Therefore, while a stereoscopic image by the holography technique uses, as an information medium, light waves with which information from a physical solid can be regarded as continuous information, a light beam reproduction technique is available wherein such light waves are discretized such that a situation theoretically equivalent to a field formed from light waves in the real world is reproduced with light beams to generate a stereoscopic image. The stereoscopic image technique called light beam reproduction method or integral photography method belongs to the light beam reproduction technique.
In the light beam reproduction technique, a light beam group composed of a large number of light beams propagating in many directions is scattered into a space by optical means in advance. Then, those light beams which are to be propagated from a virtual physical solid surface disposed at an arbitrary position are selected from the light beam group, and modulation of the intensity or phase of the selected light beams is performed to generate an image formed from the light beams in the space. An observer can observe the image as a stereoscopic image. The stereoscopic image by the light beam reproduction method is formed at an arbitrary point from multiple images from a plurality of directions and can be observed in a different manner depending upon the position from which the stereoscopic image is observed similarly as in the case wherein a three-dimensional physical solid in the real world is observed.
As an apparatus for implementing the light beam reproduction described above, an apparatus has been proposed which utilizes a combination of a display device such as a liquid crystal display device or a plasma display device and a microlens array or a pin-hole array. Also an apparatus has been proposed which includes a large number of projectors juxtaposed with each other. FIG. 29 shows an example of a configuration of a three-dimensional display apparatus which implements light beam reproduction using projectors. Referring to FIG. 29, the apparatus shown includes a large number of projector units 101 disposed in a juxtaposed relationship in a vertical direction and a horizontal direction. Light beams are emitted at different angles from each of the projector units 101. With the apparatus, images of multiple visual angles are multiple reproduced at an arbitrary point in a certain sectional plane 102 thereby to implement a stereoscopic image.
In the stereoscopic display by such a light beam reproduction method as described above, it is necessary to reproduce a large number of parallax images simultaneously, and the amount of information increases in proportion to the number of parallaxes. Japanese Patent Laid-Open No. 2004-32273 (hereinafter referred to as Patent Document 1) discloses an image display system which uses the light beam reproduction method to carry out stereoscopic display. The image display system includes a plurality of parallel image display sections each for displaying part of parallax images, and moving picture image information in a compression coded form is sent as parallax images to each of the parallax image display sections so that a large number of parallax images can be reproduced.